Dissertation Defence: Terahertz Characterisations and Analyses of Additive Manufacturing Materials and Structures

Charles Harrison Brodie, supervised by Dr. Christopher Collier, will defend their dissertation titled “Terahertz Characterisations and Analyses of Additive Manufacturing Materials and Structures” in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Electrical Engineering.

An abstract for Charles Harrison Brodie’s dissertation is included below.

Examinations are open to all members of the campus community as well as the general public. Registration is not required for in person exams.

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ABSTRACT

Assembly of free-space terahertz (THz) research instrumentation systems necessitate the use of application specific THz compatible optical components. The development, procurement, and expense of THz compatible optical components can be prohibitive for research stakeholders. Commercial three-dimensional (3D) printing (i.e., additive manufacturing) systems are investigated in this thesis, with regard to filament material selection and component fabrication, to address the accessibility of THz compatible optical components. The availability of emerging 3D printing filament materials increases year over year, prompting a need for literature to keep abreast with material characterisations of absorptive and refractive properties over the THz regime. This literature gap is rectified via a consolidative and comprehensive THz time-domain spectroscopy measurement study performed on twenty-four 3D printing filament materials. Optimal filament materials selected for use in THz compatible optical components are identified, being high impact polystyrene (HIPS) and cyclic olefin copolymer (COC), and are demonstrated as 3D printed THz Bragg structures (interference filters). The potential frequency-domain performance and tuneability of THz Bragg structures, fabricated with a commercial 3D printer, is demonstrated and characterised. The 3D printed THz Bragg structure characterisation is evaluated with finite-difference time-domain electromagnetic simulations and with a free-space THz experimental testbed. The absorptive effects of filament material selection are considered for THz Bragg structures with and without optical path equalization (i.e., responses of THz Bragg structures versus THz Bragg superstructures). The effect of commercial 3D printer Z-axis fabrication resolution is shown for the 3D printed THz Bragg structures. Frequency-domain stop-band metrics are analysed in terms of transmission loss, bandwidth, and frequency placement. Terahertz Bragg structures and superstructures fabricated from COC filament material demonstrate the potential for widespread rapid prototyping of THz compatible optical components.